Human pancreatic ribonuclease has been purified from tissue obtained at autopsy. The enzyme will be charcterized in comparison with the well-studied bovine pancreatic RNase, with particular attention to enzyme mechanism and specificity, physical properties, and immunological relatedness. Antibodies directed against the human pancreatic enzyme will be used to quantitate cross-reacting protein in extracts of other human tissues, and to compare the structrue of the enzyme to pancreatic ribonucleases of other organisms. A radioimmunoassay procedure will be used to measure circulating levels of pancreatic RNase in the serum of individuals with pancreatic cancer and related diseases. It is hoped that it will then be possible to resolve the dispute over the value of ribonuclease assays in the detection of pancreatic cancer, and perhaps to develop a practical and useful technique for the early detection of pancreatic carcinoma.